Method and apparatus for allocating resources of a control channel in a mobile communication system using orthogonal frequency division multiplexing

ABSTRACT

Methods and apparatuses are provided for wireless communication. Control symbols are mapped to a plurality of resource element groups (REGs) which is not assigned to a physical channel format indication channel (PCFICH) or a physical hybrid automatic repeat request indicator channel (PHICH). The REGs are allocated based on a time first manner. The mapped control symbols are transmitted on a packet dedicated control channel (PDCCH). A number of a plurality of resource elements (REs) in each of the REGs depends on an index of an orthogonal frequency division multiplexing (OFDM) symbol and a number of configured reference signals.

PRIORITY

This application is a Continuation of U.S. application Ser. No.14/601,795, filed in the U.S. Patent and Trademark Office (USPTO) onJan. 21, 2015, which is a Continuation of U.S. application Ser. No.13/532,226, filed in the USPTO on Jun. 25, 2012, now U.S. Pat. No.8,953,552, issued on Feb. 10, 2015, which is a Continuation of U.S.application Ser. No. 12/244,445, filed in the USPTO on Oct. 2, 2008, nowU.S. Pat. No. 8,208,438, issued on Jun. 26, 2012, which claims priorityto a Korean Intellectual Property Office on Oct. 2, 2007 and assignedSerial No. 10-2007-0099537, a Korean Patent Application filed in theKorean Intellectual Property Office on Nov. 20, 2007 and assigned SerialNo. 10-2007-0118847, and a Korean Patent Application filed in the KoreanIntellectual Property Office on Jan. 2, 2008 and assigned Serial No.10-2008-0000400, the disclosures of all of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a method and apparatus forallocating resources of a physical channel in a communication systemusing Orthogonal Frequency Division Multiplexing (OFDM), and inparticular, to a method and apparatus for allocating resources of adownlink control channel.

2. Description of the Related Art

Recently, in mobile communication systems, intensive research has beenconducted on Orthogonal Frequency Division Multiplexing (OFDM) as ascheme useful for high-speed data transmission on wire/wirelesschannels. OFDM, a scheme for transmitting data using multiple carriers,is a kind of Multi-Carrier Modulation (MCM) that converts a serial inputsymbol stream into parallel symbols, and modulates each of the parallelsymbols with multiple orthogonal frequency tones, or multiple orthogonalsubcarrier channels before transmission of the parallel symbols.

The MCM-based system was first applied to military high-frequency radiosin the late 1950s, and OFDM, which overlaps multiple orthogonalsubcarriers, has been in development since the 1970s. However,application of OFDM to actual systems was limited due to thedifficulties in realizing orthogonal modulation between multiplecarriers. However, Weinstein et al. showed in 1971 that OFDM-basedmodulation/demodulation can be efficiently processed using DiscreteFourier Transform (DFT), and remarkable technical developments in OFDMhave been made over time. Additionally, as OFDM uses a guard interval,and a scheme of inserting a Cyclic Prefix (CP) into the guard intervalis known, the OFDM system has noticeably reduced the negative influencefor the system's multipath and delay spread.

Owing to such technical developments, OFDM technology is widely appliedto digital transmission technologies such as Digital Audio Broadcasting(DAB), Digital Video Broadcasting (DVB), Wireless Local Area Network(WLAN) and Wireless Asynchronous Transfer Mode (WATM), i.e., OFDM, whichwas not widely used, due to hardware complexity, can now be realizedwith the recent development of various digital signal processingtechnologies, including Fast Fourier Transform (FFT) and Inverse FastFourier Transform (IFFT).

OFDM, although similar to the conventional Frequency DivisionMultiplexing (FDM), is characterized in that OFDM can obtain the optimaltransmission efficiency during high-speed data transmission by keepingthe orthogonality between multiple tones during the transmission.Additionally, OFDM, having a high frequency efficiency and robustnessagainst multi-path fading, can obtain an optimal transmission efficiencyduring high-speed data transmissions. OFDM provides several otheradvantages. Since OFDM overlaps frequency spectra, OFDM has a highfrequency efficiency, is robust against frequency-selective fading, andimpulse noises, can reduce an Inter-Symbol Interference (ISI) influenceusing the guard interval, and enables simple designs of hardwareequalizers. Therefore, there is an increasing tendency for OFDM to beactively used for communication system configurations.

In wireless communications, high-speed, high-quality, data services arehindered mainly due to channel environments. The channel environmentsare subject to frequent change, not only due to Additive White GaussianNoise (AWGN), but also due to a received signal's power variation causedby a fading phenomenon, shadowing, a Doppler effect based on movementand frequent velocity change of a terminal, and interference to/fromother users and multipath signals. Therefore, in order to supporthigh-speed, high-quality data services in wireless communications, thereis a need to effectively address impeding factors.

In OFDM, a modulation signal is transmitted via allocatedtwo-dimensional time-frequency resources. Resources on the time domainare classified into different OFDM symbols, and the OFDM symbols areorthogonal to each other. Resources on the frequency domain areclassified into different tones, and the tones are also orthogonal toeach other, i.e., in OFDM, it is possible to indicate a unit resource byappointing a particular OFDM symbol on the time domain and a particulartone on the frequency domain, and the unit resource is called a ResourceElement (RE). As different REs are orthogonal to each other, even thoughthey experience a selective channel, signals transmitted on differentREs can be received without mutual interference.

A physical channel is a channel of a physical layer that transmits amodulation symbol obtained by modulating at least one coded bit stream.An Orthogonal Frequency Division Multiple Access (OFDMA) systemgenerates and transmits multiple physical channels according to the useof a transmission information stream or the receiver. A transmitter anda receiver should previously agree on the rule for determining for whichREs the transmitter and receiver will arrange one physical channelduring transmission of the REs, and this rule is called ‘mapping’.

Mapping rules may vary according to the application feature of theparticular physical channel. When the transmitter maps a physicalchannel using a scheduler to increase the system's transmissionefficiency in the state where the transmitter perceives a state of areceived channel, it is preferable to arrange one physical channel on aset of REs having similar channel states, and when the transmitter mapsa physical channel, while aiming to decrease a reception error rate inthe state where the transmitter fails to perceive a state of thereceived channel, it is preferable to arrange one physical channel on aset of REs expected to have very different channel states. The formerscheme is mainly suitable for cases where the transmitter transmits datafor one user who is insusceptible to a time delay, and the latter schemeis mainly suitable for cases where the transmitter transmits data orcontrol information for one user who is susceptible to the time delay,or transmits data or control information to a plurality of users. Thelatter scheme uses resources having different channel states in order toobtain diversity gain, and within one OFDM symbol, frequency diversitygain can be obtained by mapping a physical channel to subcarriers thatare spaced as far apart as possible on the frequency domain.

Recently, in the 3rd Generation Partnership Project (3GPP), astandardization work for a radio link between a Node B (also known as aBase Station (BS)) and a User Equipment (UE; also known as a MobileStation (MS)) has been conducted in the name of a Long Term Evolution(LTE) system. The LTE system is most characterized by adopting OFDMA andSingle Carrier Frequency Domain Multiple Access (SC-FDMA) asmultiplexing schemes of the downlink and the uplink, respectively. Thepresent invention proposes a method for mapping control channels of theLTE downlink to REs.

FIG. 1 illustrates a subframe structure in a general LTE system.

One Resource Block (RB) is composed of 12 tones in the frequency domainand 14 OFDM symbols in the time domain. RB #1 111 represents the firstRB, and FIG. 1 shows a bandwidth composed of a total of K RBs from RB #1111 to RB #K 113. In the time domain, 14 OFDM symbols constitute onesubframe 117, and become a basic unit of resource allocation in the timedomain. One subframe 117 has a length of, for example, 1 ms, and iscomposed of two slots 115.

A Reference Signal (RS), which is agreed upon with a Node B so that a UEcan perform channel estimation, is transmitted, and RS0 100, RS1 101,RS2 102 and RS3 103 are transmitted from antenna ports #1, #2, #3 and#4, respectively. If only one transmit antenna port is used, RS1 101 isnot used for transmission, and RS2 102 and RS3 103 are used fortransmission of data or control signal symbols. If two transmit antennaports are defined, RS2 102 and RS3 103 are used for transmission of dataor control signal symbols.

On the frequency domain, though the absolute positions of REs where RSsare arranged are set differently for each cell, a relative intervalbetween RSs is kept constant, i.e., RSs for the same antenna portmaintain a 6-RE interval, and a 3-RE interval is maintained between RS0100 and RS1 101, and between RS2 102 and RS3 103. The absolute positionsof RSs are set differently for each cell in order to avoid inter-cellcollision of RSs.

Meanwhile, a control channel is disposed in the forefront of onesubframe on the time domain. In FIG. 1, reference numeral 119 shows aregion where a control channel can be disposed. A control channel can betransmitted over L leading OFDM symbols of a subframe, where L=1, 2 and3. When the control channel can be sufficiently transmitted with oneOFDM symbol as an amount of data to be transmitted is small, only 1leading OFDM symbol is used for control channel transmission (L=1), andthe remaining 13 OFDM symbols are used for data channel transmission.When the control channel uses 2 OFDM symbols, only 2 leading OFDMsymbols are used for control channel transmission (L=2), and theremaining 12 OFDM symbols are used for data channel transmission. Whenthe control channel uses all of 3 OFDM symbols as the amount of data tobe transmitted is large, 3 leading OFDM symbols are used for controlchannel transmission (L=3), and the remaining 11 OFDM symbols are usedfor data channel transmission.

The reason for disposing the control channel in the forefront of asubframe is to allow a UE to determine whether the UE will perform adata channel reception operation by first receiving the control channeland perceiving the existence of a data channel transmitted to the UEitself. Therefore, if there is no data channel transmitted to the UEitself, the UE has no need to perform data channel reception, making itpossible to save the power consumed in the data channel receptionoperation.

The downlink control channel, defined by the LTE system, includes aPhysical Channel Format Indication CHannel (PCFICH), a Physical H-ARQ(Hybrid-Automatic Repeat reQuest) Indicator Channel (PHICH), and aPacket Dedicated Control CHannel (PDCCH). A PCFICH is a physical channelfor transmitting Control Channel Format Indicator (CCFI) information.CCFI is 2-bit information for indicating a region L where the controlchannel can be disposed. Because the UE cannot receive the controlchannel until the first receives CCFI, PCFICH is a channel that all UEsmust first receive in the subframe, except when downlink resources arefixedly (persistently) allocated. Further, since the UE cannot know theregion L before the UE receives PCFICH, PCFICH should be transmitted inthe first OFDM symbol. A PHICH is a physical channel for transmitting adownlink ACK/NACK signal. A UE receiving a PHICH is a UE that isperforming data transmission on the uplink. Therefore, the number ofPHICHs is proportional to the number of UEs that are now performing datatransmission on the uplink. The PHICH is transmitted in the first OFDMsymbol (L_(PHICH)=1), or transmitted over three OFDM symbols(L_(PHICH)=3). L_(PHICH) is a parameter defined for every cell, and fora large-sized cell, since there is difficulty in transmitting the PHICHonly with one OFDM symbol, the parameter L_(PHICH) is introduced toadjust it. PDCCH is a physical channel for transmitting data channelallocation information or power control information.

For the PDCCH, a channel coding rate can be differently set according toa channel state of a UE that receives the PDCCH. Since the PDCCH fixedlyuses Quadrature Phase Shift Keying (QPSK) as a modulation scheme, theamount of resources used by one PDCCH should be changed in order tochange the channel coding rate. A high channel coding rate is applied toa UE having a good channel state to reduce the amount of resources used.However, a low channel coding rate is applied to a UE having a poorchannel state even though the amount of resources used is increased,thus enabling normal reception. The amount of resources consumed byindividual PDCCHs is determined in units of Control Channel Elements(CCEs). For a UE having a good channel state, the PDCCH is composed ofonly one CCE, and for a UE having a poor channel state, the PDCCH isgenerated using a maximum of 8 CCEs. The number of CCEs used forgenerating one PDCCH is one of 1, 2, 4 and 8. One CCE is composed of aset of N_(CCE) mini-CCEs. A mini-CCE is a set of 4 consecutive REsexcept for the RE used for an RS on the frequency domain. For N_(CCE)=9,the number of REs used for generating one PDCCH is one of 36, 72, 144and 288.

A mini-CCE is a basic unit of resources constituting a PCFICH and aPHICH. The PCFICH and the PHICH use a predetermined amount of resources,and in order to ease the application of multiplexing with PDCCH andtransmission diversity, the amount of resources is determined as a setof mini-CCEs. One PCFICH is generated using N_(PCFICH) mini-CCEs, andone PHICH is generated using N_(PHICH) mini-CCEs. For N_(PCFICH)=4 andN_(PHICH)=3; the PCFICH uses 16 REs and the PHICH uses 12 REs.

In order to multiplex several ACK/NACK signals, the PHICH employs a CodeDivision Multiplexing (CDM) technique. Four PHICHs are CDM-multiplexedto one mini-CCE, and are repeatedly transmitted so that the PHICHs arespaced as far apart as by N_(PHICH) on the frequency domain in order toobtain frequency diversity gain. Therefore, with a use of N_(PHICH)mini-CCEs, 4 or less PHICHs can be generated. In order to generate morethan 4 PHICHs, another N_(PHICH) mini-CCEs should be used. If therequired number of PHICHs is M, ceil(M/4)×N_(PHICH) mini-CCEs, i.e.,4×ceil(M/4)×N_(PHICH) REs, are used. Here, ceil(x) is a ceiling functionused for calculating the minimum integer greater than or equal to x.

In the mobile communication system using OFDM, a description of whichhas been made with reference to the LTE system, the conventionalresource allocation scheme for transmitting a downlink control channelis as follows: When allocation of an RE set for transmission of acontrol channel is completed in the entire frequency band of the firstOFDM symbol period, allocation of an RE set for transmission of acontrol channel is performed in the entire frequency band of the secondOFDM symbol period. In this manner, in the conventional resourceallocation scheme, resource allocation for an RE set is performed in afrequency-first manner in each OFDM symbol period used for transmissionof a control channel.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the problemsand/or disadvantages and to provide at least the advantages describedbelow. Accordingly, the present invention provides a method andapparatus for performing resource allocation on a downlink controlchannel in a time-first manner in a mobile communication system usingOFDM.

Further, the present invention provides a resource allocation method andapparatus for a control channel, for improving diversity gain in amobile communication system using OFDM.

In addition, the present invention provides a method and apparatus forperforming resources allocation on a PDCCH in a downlink of an LTEsystem in a time-first manner.

According to one aspect of the present invention, a method is providedfor wireless communication. Control symbols are mapped to a plurality ofresource element groups (REGs) which is not assigned to a PCFICH or aPHICH. The REGs are allocated based on a time first manner. The mappedcontrol symbols are transmitted on a PDCCH. A number of a plurality ofREs in each of the REGs depends on an index of an OFDM symbol and anumber of configured reference signals.

According to another aspect of the present invention, an apparatus forwireless communication. The apparatus includes a controller configuredto control operations of: mapping control symbols to a plurality of REGswhich is not assigned to a PCFICH or a PHICH, where the REGs areallocated based on a time first manner; and transmitting the mappedcontrol symbols on a PDCCH. The apparatus also includes a transmitterconfigured to transmit the mapped control symbols on the PDCCH. A numberof a plurality of REs in each of the REGs depends on an index of an OFDMsymbol and a number of configured reference signals.

According to an additional aspect of the present invention, a method isprovided for wireless communication. A control signal is received on aPDCCH. Control symbols mapped to a plurality of REGs are obtained fromthe received control signal. The REGs are not assigned to a PCFICH or aPHICH and are allocated based on time first manner. A number of aplurality of REs in each of the REGs depends on an index of an OFDMsymbol and a number of configured reference signals.

According to a further aspect of the present invention, an apparatus isprovided for wireless communication. The apparatus includes a receiverconfigured to receive a control signal on a PDCCH. The apparatus alsoincludes a controller configured to control an operation of obtainingcontrol symbols mapped to REGs from the received control signal. TheREGs are not assigned to a PCFICH or a PHICH and are allocated based ontime first manner. A number of a plurality of REs in each of the REGsdepends on an index of an OFDM symbol and a number of configuredreference signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a diagram illustrating a subframe structure in a general LTEsystem;

FIG. 2 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=4 and L=3 according to an exemplary embodiment ofthe present invention;

FIG. 3 is a diagram illustrating a control resource block and a mini-CCEindexing method for N_(ant)=4 and L=3 according to an exemplaryembodiment of the present invention;

FIG. 4 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=2 and L=3 according to an exemplary embodiment ofthe present invention;

FIG. 5 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=1 and L=3 according to an exemplary embodiment ofthe present invention;

FIG. 6 is a diagram illustrating a control resource block and a mini-CCEindexing method for N_(ant)=1 or 2 and L=3 according to an exemplaryembodiment of the present invention;

FIG. 7 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=4 and L=2 according to an exemplary embodiment ofthe present invention;

FIG. 8 is a diagram illustrating a control resource block and a mini-CCEindexing method for N_(ant)=4 and L=2 according to an exemplaryembodiment of the present invention;

FIG. 9 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=2 and L=2 according to an exemplary embodiment ofthe present invention;

FIG. 10 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=1 and L=2 according to an exemplary embodiment ofthe present invention;

FIG. 11 is a diagram illustrating a control resource block and amini-CCE indexing method for N_(ant)=1 or 2 and L=2 according to anexemplary embodiment of the present invention;

FIG. 12 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=2 and L=1 according to an exemplary embodiment ofthe present invention;

FIG. 13 is a diagram illustrating mini-CCE indexes in a control resourceblock #0 for N_(ant)=1 and L=1 according to an exemplary embodiment ofthe present invention;

FIG. 14 is a diagram illustrating a control resource block and amini-CCE indexing method for L=1 according to an exemplary embodiment ofthe present invention;

FIG. 15 is a diagram illustrating an embodiment of regular-gap resourceselection according to an exemplary embodiment of the present invention;

FIG. 16 is a diagram illustrating an embodiment of zone-based resourceselection according to an exemplary embodiment of the present invention;

FIG. 17 is a diagram illustrating another embodiment of zone-basedresource selection according to an exemplary embodiment of the presentinvention;

FIG. 18 is a diagram illustrating an embodiment of resource-mapping fora control channel for N_(ant)=4, L=3, and L_(PHICH)=1 according to anexemplary embodiment of the present invention;

FIG. 19 is a diagram illustrating an embodiment of mapping PCFICH andPHICH, generating CCEs from the remaining mini-CCEs, and mapping PDCCHresources according to an exemplary embodiment of the present invention;

FIG. 20 is a diagram illustrating a flowchart illustratingresource-mapping and demapping for a control channel, proposed by thepresent invention according to an exemplary embodiment of the presentinvention;

FIG. 21 is a diagram illustrating a transmitter structure of a Node B,to which the resource-mapping proposed by the present invention isapplied according to an exemplary embodiment of the present invention;

FIG. 22 is a diagram illustrating a UE's receiver structure to which theresource-mapping proposed by the present invention is applied accordingto an exemplary embodiment of the present invention;

FIG. 23 is a diagram illustrating an embodiment of control channelresource-mapping for N_(ant)=1 or 2, L=2, and L_(PHICH)=2 according toan exemplary embodiment of the present invention; and

FIG. 24 is a diagram illustrating an embodiment of control channelresource-mapping for N_(ant)=4, L=3, and L_(PHICH)=3 according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Preferred embodiments of the present invention will now be described indetail with reference to the annexed drawings. In the followingdescription, a detailed description of known functions andconfigurations incorporated herein has been omitted for clarity andconciseness. Terms used herein are defined based on functions in thepresent invention and may vary according to users, operators' intentionor usual practices. Therefore, the terms should be defined according tocontents throughout the specification.

For a better understanding of the present invention, a description ofthe present invention will be made herein separately for mini-CCEindexing, resource-mapping for a physical channel, and resource-mappingfor a control channel. Particularly, in a description of mini-CCEindexing, the number N_(ant) of antenna ports and the number L of OFDMsymbols used for a control channel will be described in detail for abetter understanding. The present invention indexes mini-CCEs in atime-first manner, maps them to a physical channel by regular-gapresource selection or zone-based resource selection, and then maps acontrol channel such as a PCFICH, a PHICH and a PDCCH to the physicalchannel.

Mini-CCE Indexing

In order to define a rule for determining for which control channelusing individual mini-CCEs, or physical resources, a method for indexingmini-CCEs is first defined. A mini-CCE indexing method is defineddifferently according to the number N_(ant) of antenna ports and thenumber L of OFDM symbols used for a control channel, and applies incommon a rule for indexing two-dimensional mini-CCEs first on the timedomain.

With reference to FIGS. 2 to 14, a detailed description will be made ofvarious examples of resource allocation for a control channel in anOFDM-based mobile communication system according to an embodiment of thepresent invention.

FIG. 2 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=4 and L=3.

The term ‘control resource block’, as used herein, refers to a set ofresources composed of 12 REs on the frequency domain and L OFDM symbolson the time domain. The 12 REs are equal in number to frequency-domainresources constituting one RB. Assuming that there is almost nodifference in channel response within one RB, the LTE system defines 12frequency-domain REs constituting one RB, as one RB. It can beconsidered that there is almost no difference in channel response withina control resource block based on this assumption. Although positions ofRSs in FIG. 2 can vary according to the definition given by a cell, thevariance exerts no influence on the mini-CCE indexing.

As illustrated in FIG. 2, for N_(ant)=4 and L=3, one control resourceblock includes 7 mini-CCEs. Reference numeral 200 indicates a mini-CCE#0. One mini-CCE should be composed of 4 valid REs, and since 2 REs areused for RS0 and RS1 in the mini-CCE #0, the mini-CCE #0 is composed of6 REs, including RSs. When time-first indexing is applied, the nextmini-CCE is a mini-CCE #1 201 disposed in the next OFDM symbol.Similarly, since 2 REs are used for RS2 and RS3, the mini-CCE #1 iscomposed of 6 REs, including RSs. A mini-CCE #2 202 is disposed in thenext OFDM symbol. In the subframe, since no RS is defined in the thirdOFDM symbol, 4 REs constitute one mini-CCE purely. A mini-CCE #3 203 isdisposed in the same OFDM symbol as that of the mini-CCE #2 202.Similarly, when the time-first indexing rule is applied, mini-CCEs #4204, #5 205 and #6 206 are disposed in the first, second and third OFDMsymbols, respectively, and the mini-CCE #4 204 and the mini-CCE #5 205each include 6 REs due to the RSs.

FIG. 3 illustrates a control resource block and a mini-CCE indexingmethod for N_(ant)=4 and L=3. The mini-CCE indexing method within onecontrol resource block is explained hereinabove regarding FIG. 2, andthe method in which mini-CCEs are indexed over the entire system band isdescribed regarding FIG. 3. Mini-CCE indexes in a control resource block#0 210 are equal to the mini-CCE indexes in FIG. 2, and a controlresource block #1 211 is also subjected to mini-CCE indexing in the samemanner. In a generalized description of mini-CCE indexes, a total of 7mini-CCEs of mini-CCE #7K to mini-CCE #(7K+6) are defined in a controlresource block #K 213 in the order of 220, 221, 222, 223, 224, 225 and226. Among the mini-CCEs, the mini-CCEs 220 and 224 are disposed in thefirst OFDM symbol, the mini-CCEs 221 and 225 are disposed in the secondOFDM symbol, and the mini-CCEs 222, 223, and 226 are disposed in thethird OFDM symbol. It is possible to determine in which OFDM symbol aparticular mini-CCE is disposed, by calculating the remainder obtainedby dividing the corresponding mini-CCE index by 7. If the remainder is 0or 4, the corresponding mini-CCEs are disposed in the first OFDM symbol.If the remainder is 1 or 5, the corresponding mini-CCEs are disposed inthe second OFDM symbol. If the remainder is 2, 3 or 6, correspondingmini-CCE is disposed in the third OFDM symbol.

Time-first indexing uses the characteristic that as a difference betweentwo mini-CCE indexes increases, the corresponding mini-CCEs are spacedfarther apart from each other in the frequency domain. Therefore, inlater defining a mapping rule, by generating one physical channel withmini-CCEs having a greater index difference, it is possible to maximallyobtain frequency diversity gain.

FIG. 4 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=2 and L=3. A difference from FIG. 2 is that since no RS isdefined in the second OFDM symbol, mini-CCEs 301, 303 and 306, which aredisposed in the second OFDM symbol, are each composed of 4 REs. Thecontrol resource block #0 210 includes a total of 8 mini-CCEs, and issubjected to time-first indexing in the same manner, so that themini-CCEs of mini-CCE #0 to mini-CCE #7 are indexed in the order of 300,301, 302, 303, 304, 305, 306 and 307.

FIG. 5 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=1 and L=3. Though only RS0 is needed as only one antenna port isdefined, since RS1 is punctured, the positions of and the number ofvalid REs actually available for mini-CCE generation are equal to thenumber of valid REs of the case where two antenna ports are defined.Therefore, even though the number of antenna ports is different from thenumber of antenna ports of FIG. 4, the mini-CCE indexes are equal to themini CCE indexes of FIG. 4. The mini-CCEs #0 to #7 are indexed in theorder of 310, 311, 312, 313, 314, 315, 316 and 317.

FIG. 6 illustrates a control resource block and a mini-CCE indexingmethod for N_(ant)=1 or 2 and L=3. The mini-CCE indexing method withinone control resource block has been introduced in FIGS. 4 and 5, and themethod in which mini-CCEs are indexed over the entire system band isdescribed in FIG. 6. Mini-CCE indexes in the control resource block #0210 are equal to the mini-CCE indexes in FIGS. 4 and 5, and a controlresource block #1 211 is also subjected to mini-CCE indexing in the samemanner. In a generalized description of mini-CCE indexes, a total of 8mini-CCEs of mini-CCE #8K to mini-CCE #(8K+7) are defined in a controlresource block #K 213 in the order of 330, 331, 332, 333, 334, 335, 336and 337. Among them, the mini-CCEs 330 and 335 are disposed in the firstOFDM symbol, the mini-CCEs 331, 333 and 336 are disposed in the secondOFDM symbol, and the mini-CCEs 332, 334, 337 are disposed in the thirdOFDM symbol. It is possible to determine in which OFDM symbol aparticular mini-CCE is disposed, by calculating the remainder obtainedby dividing the corresponding mini-CCE index by 8. If the remainder is 0or 5, the corresponding mini-CCEs are disposed in the first OFDM symbol.If the remainder is 1, 3 or 6, the corresponding mini-CCEs are disposedin the second OFDM symbol. If the remainder is 2, 4 or 7, thecorresponding mini-CCEs are disposed in the third OFDM symbol.

FIG. 7 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=4 and L=2. One control resource block includes 4 mini-CCEs. Thecontrol resource block #0 210 is subjected to time-first indexing, andmini-CCEs of mini-CCE #0 to mini-CCE #3 are indexed in the order of 400,401, 402 and 403. As all mini-CCEs include RSs, it can be noted that themini-CCEs each are composed of 6 REs.

FIG. 8 illustrates a control resource block and a mini-CCE indexingmethod for N_(ant)=4 and L=2. The mini-CCE indexing method within onecontrol resource block has been introduced in FIG. 7, and method inwhich mini-CCEs are indexed over the entire system band is describedregarding FIG. 8. Mini-CCE indexes in the control resource block #0 210are equal to the mini-CCE indexes in FIG. 7, and a control resourceblock #1 211 is also subjected to mini-CCE indexing in the same manner.In a generalized description of mini-CCE indexes, a total of 4 mini-CCEsof mini-CCE #4K to mini-CCE #(4K+3) are defined in a control resourceblock #K 213 in the order of 400, 401, 402 and 403. Among the mini CCEs,the mini-CCEs 400 and 402 are disposed in the first OFDM symbol, and themini-CCEs 401 and 403 are disposed in the second OFDM symbol. It ispossible to determine in which OFDM symbol a particular mini-CCE isdisposed, by calculating the remainder obtained by dividing thecorresponding mini-CCE index by 4. If the remainder is 0 or 2, thecorresponding mini-CCEs are disposed in the first OFDM symbol. If theremainder is 1 or 3, the corresponding mini-CCEs are disposed in thesecond OFDM symbol.

FIG. 9 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=2 and L=2. A difference from FIG. 7 is in that since no RS isdefined in the second OFDM symbol, mini-CCEs 501, 502 and 504 disposedin the second OFDM symbol are each composed of 4 REs. The controlresource block #0 210 includes a total of 5 mini-CCEs, and is subjectedto time-first indexing in the same manner, so that mini-CCEs of mini-CCE#0 to mini-CCE #4 are indexed in the order of 500, 501, 502, 503 and504.

FIG. 10 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=1 and L=2. Though only RS0 is needed as only one antenna port isdefined, since RS1 is punctured, the positions of and the number ofvalid REs actually available for mini-CCE generation are equal to thenumber of valid REs in the case where two antenna ports are defined.Therefore, even though the number of antenna ports is different from thenumber of antenna ports of FIG. 9, the mini-CCE indexes are equal to themini-CCE indexes of FIG. 9. The mini-CCEs of mini-CCE #0 to mini-CCE #4are indexed in the order of 510, 511, 512, 513 and 514.

FIG. 11 illustrates a control resource block and a mini-CCE indexingmethod for N_(ant)=1 or 2 and L=2. The mini-CCE indexing method withinone control resource block has been introduced in FIGS. 9 and 10, andhow mini-CCEs are indexed over the entire system band is described inFIG. 11. Mini-CCE indexes in the control resource block #0 210 are equalto the mini-CCE indexes in FIGS. 9 and 10, and a control resource block#1 211 is also subjected to mini-CCE indexing in the same manner. In ageneralized description of mini-CCE indexes, a total of 5 mini-CCEs ofmini-CCE #5K to mini-CCE #(5K+4) are defined in a control resource block#K 213 in the order of 530, 531, 532, 533 and 534. Among them, themini-CCEs 530 and 533 are disposed in the first OFDM symbol, and themini-CCEs 531, 532, 534 are disposed in the second OFDM symbol. It ispossible to determine in which OFDM symbol a particular mini-CCE isdisposed, by calculating the remainder obtained by dividing thecorresponding mini-CCE index by 5. If the remainder is 0 or 3, thecorresponding mini-CCEs are disposed in the first OFDM symbol. If theremainder is 1, 2 or 4, the corresponding mini-CCEs are disposed in thesecond OFDM symbol.

FIG. 12 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=2 and L=1. One control resource block includes 2 mini-CCEs.Since only one OFDM symbol is used for control channel transmission,even though it undergoes time-first indexing, the result is notdifferent from the result obtained when it is simply subjected toindexing on the frequency domain. Mini-CCEs of mini-CCE #0 and mini-CCE#1 are indexed in the order of 600 and 601. It can be appreciated thatas all mini-CCEs include RSs, mini-CCEs are both composed of 6 REs.

FIG. 13 illustrates mini-CCE indexes in a control resource block #0 forN_(ant)=1 and L=1. Although only RS0 is needed as only one antenna portis defined, since RS1 is punctured, the positions of and the number ofvalid REs actually available for mini-CCE generation are equal to thenumber of valid REs of the case where two antenna ports are defined.Therefore, even though the number of antenna ports is different from thenumber of antenna ports of FIG. 12, the mini-CCE indexes are equal tothe mini-CCE indexes of FIG. 12. The mini-CCEs of mini-CCE #0 andmini-CCE #1 are indexed in the order of 600 and 601.

FIG. 14 illustrates a control resource block and a mini-CCE indexingmethod for L=1. The mini-CCE indexing method within one control resourceblock has been introduced in FIGS. 12 and 13, and method in whichmini-CCEs are indexed over the entire system band is described in FIG.14. Mini-CCE indexes in the control resource block #0 210 are equal tothe mini-CCE indexes in FIGS. 12 and 13, and a control resource block #1211 is also subjected to mini-CCE indexing in the same manner. In ageneralized description of mini-CCE indexes, a total of 2 mini-CCEs ofmini-CCE #2K and mini-CCE #(2K+1) are defined in a control resourceblock #K 213 in the order of 630 and 631. Since only one OFDM symbol isused for control channel transmission, even though the OFDM symbolundergoes time-first indexing, the result is not different from theresult obtained when the OFDM symbol is simply subject to indexing onthe frequency domain. In this case, all mini-CCEs are disposed in thefirst OFDM symbol.

Mini-CCE indexing is described as follows: A mini-CCE is represented bythe first one of REs constituting the mini-CCE, i.e., when k indicatessubcarrier indexes on the frequency domain and l indicates OFDM symbolindexes on the time domain, one RE can be expressed with an index (k,l).Further, a mini-CCE is represented by an index (k,l) of its first RE. Ifan RB, or control resource block, including mini-CCE, starts with RS, anindex of an RE representative of the mini-CCE should be changed to(k−1,l). In this condition, an RE with an index (k−1,l) is RS. Mini-CCEindexes are based on time-first indexing, and the mini-CCEs can beindexed by a function f(k,l) that satisfies the above condition. Thefunction f(k,l), a function having, as its input, an RE (k,l)representative of the mini-CCE, indexes the corresponding mini-CCEsaccording to the values of the corresponding mini-CCEs of f(k,l).

One example of the function f(k,l) is to define f(k,l)=k+1. As describedin the above example, if a mini-CCE includes RS, k increases atintervals of 6, and if the mini-CCE includes no RS, k increases atintervals of 4. By contrast, l increases at intervals of 1. Therefore,if the time index l increases by one at the same frequency index k, thevalue of the time index l is less than a value obtained by increasingthe frequency index k by one at the same time index l. Therefore, sincethe time index-increased mini-CCE is first indexed compared with thefrequency index-increased mini-CCE, it is possible to use the functionf(k,l)=k+1 for time-first indexing. It is possible to define variousother functions f(k,l) that realize time-first indexing. A descriptionof all the functions will be omitted herein.

For some mini-CCEs, even though the functions f(k,l)=k+1 of the miniCCEs use different k and l, the mini-CCEs may show the same outputs. Inthis case, it is possible to realize the above-described time-firstindexing by arranging them such that the mini-CCE with a lower frequencyindex k has an earlier index.

In brief, in indexing a mini-CCE using an index (k,l) of an RErepresenting the mini-CCE, the invention introduces a function f(k,l)satisfying the time-first indexing condition, and indexes mini-CCEs sothat a mini-CCE with a less value of f(k,l) has an earlier index, and ifthe value of f(k,l) is equal, a less-k mini-CCE has an earlier index.The RE representative of the mini-CCE can be either included or notincluded in the mini-CCE. In later resource-mapping, modulation symbolsets are arranged, each of which is composed of 4 modulation symbols inthe order of the mini-CCE indexes that underwent the indexing.

Resource Mapping for Physical Channel

The mini-CCE indexing is to index resources ease description of howresource-mapping is performed. In this section, a description will bemade as to how a physical channel is mapped to resources after theresources are indexed. The resource-mapping for a physical channelshould be performed such that modulation symbols are distributed overthe entire system band so as to maximally obtain frequency diversitygain. The present invention proposes, as a resource-mapping method forachieving this goal, a regular-gap resource selection method and azone-based resource selection method.

FIG. 15 illustrates an embodiment of regular-gap resource selection.Reference numerals 700˜710 represent individual physical resources. Theunit of physical resources can be either an RE or a set of a pluralityof adjacent REs. Herein, the unit is a mini-CCE, since the units arephysical resources used for control channel transmission, defined by theLTE system. However, if the resource-mapping for a physical channel isapplied to a channel of another type, the unit of physical resources canbe defined differently. In the embodiment of FIG. 15, a total of 11mini-CCEs are assumed to be available. In the embodiment of the presentinvention according to FIG. 15, 3 mini-CCEs are selected from the 11mini-CCEs and are used for transmission of one physical channel. FIG. 15illustrates an embodiment of selecting 3 mini-CCEs 702, 705 and 708, andgenerating one physical channel with the selected mini-CCEs. Theselected first mini-CCE 702 is spaced from a mini-CCE #0 by an offset711, and the selected remaining mini-CCEs 705 and 708 are spaced by aregular gap (interval) 713. This regular-gap resource selection can bemathematically expressed as Equation (1).n _(i)=mod(offset+i×gap,N _(total))  (1)

In Equation (1), i denotes an order of a selected mini-CCE, and if onephysical channel is composed of N_(phy) mini-CCEs, i=0, . . . ,N_(phy-1). Further, n_(i) denotes an index of an i^(th)-selectedmini-CCE. The selected first mini-CCE is an ‘offset’-th mini-CCE, andthe selected remaining mini-CCEs are mini-CCEs which are spaced by aregular gap. In addition, N_(total) denotes the number of availablemini-CCEs, and if the mini-CCE index is greater than or equal toN_(total), a modulo operation is performed so that the mini-CCE mayundergo a cyclic shift. Herein, mod(x,y) refers to the remainderobtained by dividing x by y. In order to maximally increase thefrequency interval, gap can be determined such thatgap=floor(N_(total)/N_(phy)) or gap=ceil(N_(total)/N_(phy)). Herein,floor(x) is a floor function used for calculating the maximum integerless than or equal to x, and ceil(x) is a ceiling function used forcalculating the minimum integer greater than or equal to x. If theembodiment of FIG. 15 is described with Equation (1), N_(total)=11,N_(phy)=3 offset=2, and gap=floor(N_(total)/N_(phy))=3.

FIG. 16 illustrates an embodiment of zone-based resource selection. Atotal of 11 available mini-CCEs are divided into 3 zones. A Zone #0 720is composed of 3 mini-CCEs 700, 701 and 702, a Zone #1 721 is composedof 3 mini-CCEs 703, 704 and 705, and a Zone #2 722 is composed of 5mini-CCEs 706, 707, 708, 709 and 710. The mini-CCEs 700, 703 and 706 areleading mini-CCEs of the Zone #0 720, the Zone #1 721 and the Zone #2722, respectively. One physical channel is generated by selecting amini-CCE, which is spaced from the leading mini-CCE of each zone by aparticular offset. FIG. 16 illustrates a method of generating onephysical channel by selecting a mini-CCE 702 spaced from the leadingmini-CCE 700 by an offset 0 in the Zone #0 720, selecting a mini-CCE 705spaced from the leading mini-CCE 703 by an offset 1 in the Zone #1 721,and selecting a mini-CCE 708 spaced from the leading mini-CCE 706 by anoffset 2 in the Zone #2 722. The zone-based resource selection can bemathematically expressed as Equation (2).n _(i) =s _(i)+Δ_(i)  (2)

In Equation (2), i denotes an order of a selected mini-CCE, and if onephysical channel is composed of N_(phy) mini-CCEs, i=0, . . . ,N_(phy-1). Since one mini-CCE is selected from each Zone, the number ofZones should be N_(phy). Further, s_(i) denotes a leading mini-CCE indexof a Zone #i. If a Zone #i is defined with z_(i) mini-CCEs, s₀=0, ands_(i)=s_(i−1)+z_(i−1) for i=1, . . . , N_(phy-1). Additionally, Δ_(i) isa value that indicates which mini-CCE is selected from a Zone #i, andΔ_(i)=mod(offset_(i), z_(i)). Meanwhile, offset is subject to changeaccording to a cell and a subframe by a predetermined rule. If theoffset_(i) is subject to change according to a cell, theresource-mapping is cell-specific mapping, and if the offset_(i) issubject to change according to a subframe, the resource-mapping iszone-based hopping.

The embodiment of FIG. 16 corresponds to the case of applyingz_(i)=floor(N_(total)/N_(phy))=3 to the Zone #0 720 and the Zone #1 721,and setting the remaining mini-CCE as the Zone #2 722, and thisembodiment selects mini-CCEs 702, 705 and 708 by applying offset_(i)=2for all i.

In generating one physical channel, the zone-based resource selection ischaracterized by dividing the entire system band into zones with aspecific size, the number of which is equal to the number of resourcesrequired for generating the physical channel, and by selecting onephysical resource from each zone, thereby guaranteeing frequencydiversity gain and making it possible to obtain interference diversitygain by changing a resource selection method according to a cell and asubframe. The zone-based resource selection method can define variousmethods according to how a size z_(i) of each zone is set, and accordingto how an offset_(i) is set in each zone.

FIG. 17 illustrates another embodiment of zone-based resource selection.In this embodiment, a size of each Zone is determined according to therule of Equation (3).z _(i) =s _(i+1) −s _(i), where s _(i)=floor(i*N _(total) /N _(phy)) fori=0, . . . , N _(phy-2) and s _(Nphy) =N _(total) That is, z_(i)=floor((i+1)*N _(total) /N _(phy))−floor(i*N _(total) /N _(phy)) fori=0, . . . , N _(phy-2) z _(Nphy-1) =N _(total)−floor((N _(phy-1))*N_(total) /N _(phy))  (3)

According to the above rule, a Zone #0 730 is composed of 3 mini-CCEs700, 701 and 702, a Zone #1 731 is composed of 4 mini-CCEs 703, 704, 705and 706, and a Zone #2 732 is composed of 4 mini-CCEs 707, 708, 709 and710. One physical channel is generated by selecting mini-CCEs 702, 705and 709 by applying offset_(i)=2 for all i.

Resource Mapping for Control Channel

In this section, a resource-mapping method for PCFICH, PHICH and PDCCH,which are downlink control channels defined by the LTE system, based onthe mini-CCE indexing and the resource-mapping rule for a physicalchannel, is described as follows:

FIG. 18 illustrates an embodiment of resource-mapping for a controlchannel for N_(ant)=4, L=3, and L_(PHICH)=1. For N_(ant)=4 and L=3,mini-CCEs are indexed as shown in FIG. 3. For convenience, in theembodiment of FIG. 18, the number of control resource blocks is assumedto be 6, so that a total of 42 mini-CCEs are defined. If the 42mini-CCEs are subjected to one-Dimensional (1D) rearrangement in theorder of the indexes of the mini-CCEs, the results are as shown byreference numeral 821. Since the PCFICH should be arranged on mini-CCEsof the first OFDM symbol, and the PHICH should also be arranged onmini-CCEs of the first OFDM symbol for L_(PHICH)=1, the embodimentshould pick out only the mini-CCEs of the first OFDM symbol in order toselect mini-CCEs for the PCFICH and mini-CCEs for the PHICH. Referencenumeral 823 shows only the mini-CCEs picked out of the first OFDMsymbol. Of the 42 mini-CCEs, 12 mini-CCEs #0 800, #4 801, #7 802, #11803, #14 804, #18 805, #21 806, #25 807, #28 808, #32 809, #35 810 and#39 811, the remainders, obtained by dividing the mini-CCE index by 7,of all of which are 0 or 4, are all disposed in the first OFDM symbol.In the state where only the mini-CCEs of the first OFDM symbol areselected and arranged as shown by reference numeral 823, the mini-CCEsfor PCFICH are first selected. Reference numeral 825 shows the mini-CCE#7 802, the mini-CCE #18 805, the mini-CCE #28 808 and the mini-CCE #39811, which are selected as 4 mini-CCEs (N_(PCFICH)=4) for a PCFICH. Theprocess of selecting mini-CCEs for PCFICH is performed according toregular-gap resource selection or zone-based resource selection, whichis the resource-mapping rule for a physical channel. In order togenerate a PHICH, it is necessary to select mini-CCEs, which aremaximally spaced apart from each other on the frequency domain, amongthe mini-CCEs unused for the PCFICH among the mini-CCEs of the firstOFDM symbol. Reference numeral 827 shows mini-CCEs unused for thePCFICH, which are rearranged according to the order of the indexes ofthe mini-CCEs, among the mini-CCEs of the first OFDM symbol. The processof selecting mini-CCEs for the PHICH is performed according toregular-gap resource selection or zone-based resource selection, whichis the resource-mapping rule for a physical channel. Reference numeral829 shows mini-CCEs selected for the PHICH. Here, PHICHs 0, 1, 2 and 3(843) are generated by selecting 3 mini-CCEs of the mini-CCE #0 800, themini-CCE #14 804 and the mini-CCE #32 809 (N_(PHICH)=3), and PHICHs 4,5, 6 and 7 (845) are generated by selecting 3 mini-CCEs of the mini-CCE#4 801, the mini-CCE #21 806 and the mini-CCE #35 810 (N_(PHICH)=3).Reference numeral 831 shows 32 mini-CCEs, which are rearranged accordingto the order of the indexes of the mini-CCEs, except for the mini-CCEsused for PCFICH and PHICH. The embodiment generates CCEs from theremaining mini-CCEs 847, and maps the PDCCH thereto.

FIG. 19 illustrates an embodiment of mapping the PCFICH and the PHICH,generating CCEs from the remaining mini-CCEs, and mapping the PDCCHresources. Reference numerals 1001˜1015 show the remaining mini-CCEs847, which are rearranged according to the order of the indexes of themini-CCEs, except for the mini-CCEs, which are selected for the PCFICHand the PHICH in FIG. 18. One CCE is generated by selecting 9 mini-CCEs(N_(CCE)=9) according to regular-gap resource selection or zone-basedresource selection, which is the resource-mapping rule for a physicalchannel. A CCE #0 1030, a CCE #1 1031 and a CCE #2 1032 are suchselected mini-CCEs. In the embodiment of FIG. 19, a PDCCH #0 1050 ismapped to the CCE #0 1030 and the CCE #1 1031, and transmitted using two2 CCEs, and a PDCCH #1 1051 is mapped to the CCE #2 1032, andtransmitted using 1 CCE. Meanwhile, since 3 CCEs are generated from theremaining 32 mini-CCEs 847, the number of mini-CCEs used for the PDCCHis 27, and 5 mini-CCEs are not used for any control channel. Themini-CCE #5 1004, the mini-CCE #11 1009 and the mini-CCE #25 1012represent such mini-CCEs, which are not selected for CCEs.

In mapping the PCFICH and the PHICH, and generating CCEs from theremaining mini-CCEs, if one CCE is generated by selecting mini-CCEshaving a great index gap, there is a very high possibility thatmini-CCEs constituting individual CCEs will be spaced apart from eachother on the frequency domain, making it possible to obtain frequencydiversity gain.

FIG. 20 illustrates a flowchart illustrating resource-mapping anddemapping for a control channel, proposed by the present invention.

In step 901, mini-CCEs are indexed (or numbered). The mini-CCE indexing(or mini-CCE numbering) is performed according to the number N_(ant) ofantenna ports and the number L of OFDM symbols used for a controlchannel, using the rules shown in FIGS. 3, 6, 8, 11, and 14.

Next, in step 903, all mini-CCEs are 1D-rearranged in the order of theindexes of the mini-CCEs determined in step 901.

In step 905, mini-CCEs disposed in the first OFDM symbol are selectedand rearranged in the order of the indexes of the mini-CCEs.

In step 907, the embodiment selects N_(PCFICH) mini-CCEs from themini-CCEs rearranged in step 905. In this process, regular-gap resourceselection or zone-based resource selection can be used, which is theresource-mapping rule for a physical channel.

In step 909, a process of a transmission apparatus maps a PCFICHmodulation symbol to the mini-CCEs for a PCFICH, selected in step 907,or a process of a reception apparatus demaps the PCFICH modulationsymbol from the mini-CCEs for the PCFICH.

In step 911, the embodiment rearranges the mini-CCEs on the first OFDMsymbol, except for the mini-CCEs used for the PCFICH, in the order ofthe indexes of the mini-CCEs.

In step 913, the embodiment selects N_(PHICH) mini-CCEs from theremaining mini-CCEs on the first OFDM symbol. In this process,regular-gap resource selection or zone-based resource selection can beused, which is the resource-mapping rule for a physical channel. Theselected mini-CCEs can be directly used as mini-CCEs for the PHICH, orcan be used for determining mini-CCEs for the PHICH. If L_(PHICH)=1, themini-CCEs selected in step 913 are directly mapped to the PHICH.However, if L_(PHICH)=3, mini-CCEs for the PHICH are not selected onlyfrom the first OFDM symbol. In order to guarantee frequency diversitygain, the embodiment first selects N_(PHICH) mini-CCEs spaced apart fromeach other on the frequency domain in the first OFDM symbol, uses someof the selected mini-CCEs for actual the PHICH, and uses the remainingmini-CCEs as a criterion for determining which mini-CCEs will beselected from another OFDM symbol and use them for the PHICH. Accordingto the mini-CCE indexing rule proposed by the present invention, if anindex of a mini-CCE disposed in the first OFDM symbol is increased byone, a mini-CCE disposed in the second OFDM symbol, which uses the samefrequency band, can be indicated. If an index of a mini-CCE disposed inthe first OFDM symbol is increased by two, a mini-CCE disposed in thethird OFDM symbol, which uses the same frequency band, can be indicated.For example, referring to FIG. 2, the mini-CCE #5 205 obtained byincreasing an index of the mini-CCE #4 204 disposed on the first OFDMsymbol by one, is disposed on the second OFDM symbol, the mini-CCE #6206 obtained by the index by two is disposed on the third OFDM symbol,and the mini-CCE #4 204, #5 205 and #6 206 all occupy the duplicatedfrequency band.

In step 914, the embodiment selects mini-CCEs for the PHICH. Inselecting mini-CCEs for the PHICH from the remaining mini-CCEs exceptfor the mini-CCEs for the PCFICH, if L_(PHICH)=1, the intact mini-CCEsselected in step 913 are used as mini-CCEs for PCFICH, and ifL_(PHICH)≠1, mini-CCEs for the PHICH based on the mini-CCEs selected instep 913. A detailed description of step 914 will be given withreference to FIGS. 23 and 24.

In step 915, a process within the transmission apparatus maps a PHICHmodulation symbol to mini-CCEs for the PHICH, selected in step 914, or aprocess of the reception apparatus demaps the PHICH modulation symbolfrom mini-CCEs for the PHICH.

In step 917, the embodiment 1D-rearranges the remaining mini-CCEs exceptfor the mini-CCEs for PCFICH and the mini-CCEs for PHICH, in the orderof the indexes of the mini-CCEs.

In step 919, the embodiment generates CCEs by gathering N_(CCE)mini-CCEs. In this process, regular-gap resource selection or zone-basedresource selection can be used, which is the resource-mapping rule for aphysical channel.

Finally, in step 921, a process within the transmission apparatus maps aPDCCH modulation symbol to the CCEs, or a process of the receptionapparatus demaps the PDCCH modulation symbol from the CCEs.

FIG. 21 illustrates a transmitter structure of a Node B, to which theresource-mapping proposed by the present invention is applied. Acontroller 953 determines a mapping rule for individual control channelsbased on cell information and the number of PHICHs, and resource-mappingfor control channel and RS according thereto is performed by means of amapper 955. To the mapper 955 are provided RS from an RS generator 931,a PCFICH modulation signal from a PCFICH signal generator 933, a PHICHmodulation signal from a PHICH signal generator 935, and a PDCCHmodulation signal from a PDCCH signal generator 947. In the PHICH signalgenerator 935, 4 PHICHs are gathered from individual PHICH signalgenerators 939 to 941 and subjected to CDM 943. Reference numerals 937and 945 represent signal generators for generating 4 PHICH signals ofPHICHs 0˜3 and PHICHs 4˜7, respectively. The PDCCH signal generator 947includes individual PDCCH signal generators 949 to 951 for generatingPDCCH signals to be transmitted to different UEs. The number of CCEsoccupied by one PDCCH is determined by the controller 953. The signal towhich control channels and RS are mapped is TDM-multiplexed, by a TimeDivision Multiplexer 959, with a signal 957 to which PDSCHs and RS aremultiplexed, and then transmitted through a transmission processingdevice 961.

FIG. 22 illustrates a UE's receiver structure to which theresource-mapping proposed by the present invention is applied. As in thetransmitter, a controller 991 determines a demapping rule for individualcontrol channels based on cell information and the number of PHICHs, andresource demapping for control channels and RS according thereto isperformed by means of a demapper 979. A received signal is firstconverted into a baseband signal by means of a reception processingdevice 971, and TDM-demultiplexed, by a Time Division Multiplexer 973,into PDSCHs and RSs on a PDSCH region, and control channels and RSs on acontrol channel region. Regarding the signal processed by the receptionprocessing device 971, RSs are separated from the PDSCHs and RSs on thePDSCH region by means of an RS demapper 977, and only RSs are separatedfrom the control channels and RS signals on the control channel regionby means of the demapper 979 (981). The RSs are provided to a channelestimator 983 where they undergo channel estimation, and the channelestimate is provided to a PDSCH receiver 995, a PCFICH receiver 985, aPHICH receiver 987 and a PDCCH receiver 989, and then used for receivinga PDSCH signal, a PCFCH signal, a PHICH signal and a PDCCH signal,respectively. If the demapper 979 separates a PCFICH modulation symbolstream and provides the results to the PCFICH receiver 985, the PCFICHreceiver 985 restores a size L of the control channel region in thecorresponding subframe, and the information is provided to thecontroller 991 and used by the demapper 979 to extract PHICH and PDCCHmodulation symbol streams. A PDSCH demapper 993 extracts a PDSCH signal,and provides the PDSCH signal to the PDSCH receiver 995, and the PDSCHreceiver 995, under the control of the controller 991, restores datachannels using allocation information of the data channels, restored bymeans of the PDCCH receiver 989.

Several other embodiments will be described in order to determine themanner in which the resource-mapping rule for control channel, proposedby the present invention, will be applied under another condition. FIGS.23 and 24 show the method in which resource-mapping for PHICH isperformed, for L_(PHICH)≠1.

FIG. 23 illustrates an embodiment of control channel resource-mappingfor N_(ant)=1 or 2, L=2, and L_(PHICH)=2. A Multicast Broadcast SingleFrequency Network (MBSFN) subframe is a subframe for operating a SingleFrequency Network (SFN), and 2 leading OFDM symbols of the subframe arefixed to a control channel and the remaining OFDM symbols are used forSFN transmission. For L_(PHICH)=1, the resource-mapping for PHICH,described in the embodiment of FIG. 18, can be applied. For L_(PHICH)≠1,although generally, L_(PHICH)=3, since L=2 especially in the MBSFNsubframe, L_(PHICH)=2. If N_(PHICH)=3, it is necessary to define a rulefor determining how 3 mini-CCEs will be selected for L_(PHICH)=2. Inorder to keep the balance of resource consumption and power consumptionbetween OFDM symbols, some PHICHs are generated by selecting 1 mini-CCEfrom the first OFDM symbol and 2 mini-CCEs from the second OFDM symbol(hereinafter ‘1+2 selection’), and some PHICHs are generated byselecting 2 mini-CCEs from the first OFDM symbol and 1 mini-CCE from thesecond OFDM symbol (hereinafter ‘2+1 selection’). When mini-CCEs for thePHICH are selected in this manner, an additional mapping rule differentfrom the rule described regarding the embodiment of FIG. 18 should bedefined. Such an additional rule has been described in steps 913 and 914of FIG. 20.

For N_(ant)=1 or 2, and L=2, the mini-CCEs are indexed as shown in FIG.11. For convenience, it is assumed in the embodiment of FIG. 23 that thenumber of control resource blocks is 6, so a total of 30 mini-CCEs aredefined. The 30 mini-CCEs are 1D-rearranged in the order of indexes ofthe mini-CCEs as shown by reference numeral 821. Since the PCFICH shouldbe arranged on mini-CCEs of the first OFDM symbol and a referencemini-CCE for selecting mini-CCEs for PHICH should also be selected fromthe mini-CCEs of the first OFDM symbol, only the mini-CCEs of the firstOFDM symbol should be picked out in order to select mini-CCEs for thePCFICH and dummy mini-CCEs for PHICH. Reference numeral 823 shows onlythe mini-CCEs picked out of the first OFDM symbol. Of the 30 mini-CCEs,12 mini-CCEs mini-CCE #0 850, #3 851, #5 852, #8 853, #10 854, #13 855,#15 856, #18 857, #20 858, #23 859, #25 860 and #28 861, the remainders,obtained by dividing the mini-CCE index by 5, of all of which are 0 or3, are all disposed in the first OFDM symbol. In the state where onlythe mini-CCEs of the first OFDM symbol are selected and arranged asshown by reference numeral 823, the mini-CCEs for the PCFICH are firstselected. Reference numeral 825 shows the mini-CCE #5 852, the mini-CCE#13 855, the mini-CCE #20 858 and the mini-CCE #28 861, which areselected as 4 mini-CCEs (N_(PCFICH)=4) for the PCFICH. The process ofselecting mini-CCEs for the PCFICH is performed according to regular-gapresource selection or zone-based resource selection, which is theresource-mapping rule for a physical channel. For reference, since L isfixed to 2 in the MBSFN subframe, the PCFICH may not be needed. Thoughsuch an exception has not yet been defined in the LTE system, if thePCFICH is not transmitted only for the MBSFN subframe, the PCFICHmini-CCE selection, step 825, and its associated steps 907 and 909 ofFIG. 20 can be omitted.

In order to generate the PHICH, it is necessary to select mini-CCEs thatare maximally spaced apart from each other on the frequency domain,among the mini-CCEs unused for the PCFICH among the mini-CCEs of thefirst OFDM symbol. The selected mini-CCEs are not directly used for thePHICH, but are used as a criterion for selecting mini-CCEs for thePHICH. Assume that such mini-CCEs are dummy mini-CCEs for PHICH mapping.Reference numeral 827 shows mini-CCEs unused for the PCFICH, which arerearranged in the order of the indexes of the mini-CCEs, among themini-CCEs of the first OFDM symbol. The process of selecting dummymini-CCEs for PHICH mapping is performed according to regular-gapresource selection or zone-based resource selection, which is theresource-mapping rule for a physical channel. The mini-CCE #3 851, themini-CCE #15 856 and the mini-CCE #25 860 are selected as dummymini-CCEs for PHICH mapping, and all of the mini-CCEs 851, 856 and 860are disposed on the first OFDM symbol. Reference numeral 829 showsmini-CCEs selected for the PHICH. Here, PHICHs 0, 1, 2 and 3 (873) aregenerated by selecting 3 mini-CCEs of the mini-CCE #3 851, the mini-CCE#16 863 and the mini-CCE #26 864 (N_(PHICH)=3), and PHICHs 4, 5, 6 and 7(875) are generated by selecting 3 mini-CCEs of the mini-CCE #4 862, themini-CCE #15 856 and the mini-CCE #25 860 (N_(PHICH)=3).

In a detailed description of the process of selecting mini-CCEs forPHICH, the mini-CCE #3 851 disposed on the first OFDM symbol among thedummy mini-CCEs for PHICH mapping is used for mapping PHICHs 0, 1, 2 and3 (873). If the PHICHs 0, 1, 2 and 3 (873) are generated in a “1+2selection” manner, the remaining two mini-CCEs should be selected fromthe second OFDM symbol. Therefore, the mini-CCE #15 856, which is theremaining dummy mini-CCE for PHICH mapping, the mini-CCE #16 863 and themini-CCE #26 864, which are obtained by increasing the index of themini-CCE #25 860 by one, are used for mapping the PHICHs 0, 1, 2 and 3(873). As described above, according to the mini-CCE indexing ruleproposed by the present invention, if an index of a mini-CCE isincreased by one, a mini-CCE disposed on the same frequency band can beindicated in the next OFDM symbol. Since the dummy mini-CCEs for thePHICH, selected from the first OFDM symbol, have already been selectedas mini-CCEs which are spaced as far as possible on the frequencydomain, the selection guarantees that the mini-CCEs of the second OFDMsymbol, selected after increasing indexes of the mini-CCEs, are alsospaced apart from each other on the frequency domain, making it possibleto obtain the same frequency diversity gain. Meanwhile, the mini-CCE #15856 and the mini-CCE #25 860 disposed on the first OFDM symbol among thedummy mini-CCEs for PHICH mapping, are used for mapping the PHICHs 4, 5,6 and 7 (875). Since the PHICHs 0, 1, 2 and 3 (873) are generated in a“1+2 selection” manner, the PHICHs 4, 5, 6 and 7 (875) are generated ina “2+1 selection” manner. This is to keep the balance of resourceconsumption and power consumption between OFDM symbols. Since 2mini-CCEs are selected from the first OFDM symbol, 1 mini-CCE isselected from the second OFDM symbol. To this end, the mini-CCE #4 862,which is obtained by increasing by one the index of the mini-CCE #3 851used for the PHICHs 0, 1, 2 and 3 (873), is selected as a mini-CCE forthe PHICHs 4, 5, 6 and 7 (875). Accordingly, the PHICHs 0, 1, 2 and 3(873) are mapped to the mini-CCE #3 851, the mini-CCE #16 863, and themini-CCE #26 864, and the PHICHs 4, 5, 6 and 7 (875) are mapped to themini-CCE #4 862, the mini-CCE #15 856 and the mini-CCE #25 860.

In summary, if dummy mini-CCEs #A, #B and #C for PHICH mapping areselected, PHICHs a˜a+3 are mapped to mini-CCEs #A, #(B+1) and #(C+1),and PHICHs a+4˜a+7 are mapped to mini-CCEs #(A+1), #B and #C. In thisway, the PHICHs a˜a+3 are generated in a “1+2 selection” manner, and thePHICHs a+4˜a+7 are generated in a “2+1 selection” manner. When there isa need for additional PHICHs, mini-CCEs for PHICH mapping are selectedby selecting other dummy mini-CCEs and repeating the same process.

In an alternative method, if dummy mini-CCEs #A, #B and #C for PHICHmapping are selected, PHICHs a˜a+3 are mapped to mini-CCEs #A, #(B+1)and #C, and PHICHs a+4˜a+7 are mapped to mini-CCEs #(A+1), #B and#(C+1). In this way, the PHICHs a˜a+3 are generated in a “2+1 selection”manner, and the PHICHs a+4˜a+7 are generated in a “1+2 selection”manner.

Reference numeral 831 shows 20 mini-CCEs, which are rearranged in theorder of the indexes of the mini-CCEs, except for the mini-CCEs used forthe PCFICHs and PHICHs. The embodiment generates CCEs from the remainingmini-CCEs 877, and maps the PDCCHs thereto.

FIG. 24 illustrates an embodiment of control channel resource-mappingfor N_(ant)=4, L=3, and L_(PHICH)=3. If L_(PHICH)=3 and N_(PHICH)=3, theembodiment should generate PHICH by selecting one mini-CCE from eachOFDM symbol. Even the mini-CCEs selected from different OFDM symbolsshould be selected such that the selected mini-CCEs are maximally spacedapart from each other on the frequency domain, in order to obtainfrequency diversity gain.

For N_(ant)=4 and L=3, mini-CCEs are indexed as shown in FIG. 3. Forconvenience, it is assumed in the embodiment of FIG. 24 that the numberof control resource blocks is 6, so a total of 42 mini-CCEs are defined.If the 42 mini-CCEs are subjected to 1D rearrangement in the order ofthe indexes of the mini-CCEs, the results are as shown by referencenumeral 821. Since the PCFICH should be arranged on mini-CCEs of thefirst OFDM symbol, and the PHICH should also be arranged on mini-CCEs ofthe first OFDM symbol for L_(PHICH)=1, the embodiment should pick outonly the mini-CCEs of the first OFDM symbol in order to select mini-CCEsfor the PCFICH and mini-CCEs for the PHICH. Reference numeral 823 showsonly the mini-CCEs picked out of the first OFDM symbol. Of the 42mini-CCEs, 12 mini-CCEs #0 880, #4 881, #7 882, #11 883, #14 884, #18885, #21 886, #25 887, #28 888, #32 889, #35 890 and #39 891, theremainders, obtained by dividing the mini-CCE index by 7, of all ofwhich are 0 or 4, are all disposed in the first OFDM symbol. In thestate where only the mini-CCEs of the first OFDM symbol are selected andarranged as shown by reference numeral 823, the mini-CCEs for the PCFICHare first selected. Reference numeral 825 shows the mini-CCE #7 882, themini-CCE #18 885, the mini-CCE #28 888 and the mini-CCE #39 891, whichare selected as 4 mini-CCEs (N_(PCFICH)=4) for the PCFICH. The processof selecting mini-CCEs for the PCFICH is performed according toregular-gap resource selection or zone-based resource selection, whichis the resource-mapping rule for a physical channel. For reference,since L_(PHICH) is fixed to 3, it cannot but use 3 leading OFDM symbolsfor control channel transmission. Therefore, CCFI information ismeaningless, and the PCFICH may not be needed. Though such an exceptionhas not yet been defined in the LTE system, if the PCFICH is nottransmitted only for L_(PHICH)=3, the PCFICH mini-CCE selection (825)and its associated steps 907 and 909 of FIG. 20 can be omitted.

In order to generate PHICH, it is necessary to select, as dummymini-CCEs for the PHICH, mini-CCEs which are maximally spaced apart fromeach other on the frequency domain, among the mini-CCEs unused forPCFICH among the mini-CCEs of the first OFDM symbol. Reference numeral827 shows mini-CCEs unused for the PCFICH, which are rearranged in theorder of the indexes of the mini-CCEs, among the mini-CCEs of the firstOFDM symbol. The process of selecting dummy mini-CCEs for PHICH mappingis performed according to regular-gap resource selection or zone-basedresource selection, which is the resource-mapping rule for a physicalchannel. The mini-CCE #4 881, the mini-CCE #21 886, the mini-CCE #35 890are selected as dummy mini-CCEs for PHICH mapping, and all of themini-CCEs 881, 886 and 890 are disposed on the first OFDM symbol.Reference numeral 829 shows mini-CCEs selected for PHICH. Here, PHICHs0, 1, 2 and 3 (1103) are generated by selecting 3 mini-CCEs of themini-CCE #4 881, the mini-CCE #22 893 and the mini-CCE #37 894, andPHICHs 4, 5, 6 and 7 (1105) are generated by selecting 3 mini-CCEs ofthe mini-CCE #5 895, the mini-CCE #23 896 and the mini-CCE #35 890.

In a detailed description of the process of selecting mini-CCEs for thePHICH, the mini-CCE #4 881 disposed on the first OFDM symbol among thedummy mini-CCEs for PHICH mapping is used for mapping PHICHs 0, 1, 2 and3 (1103). The mini-CCE #22 893, which is obtained by increasing by onean index of the mini-CCE #21 886, which is a dummy mini-CCE for PHICHmapping, in order to select one mini-CCE from the second OFDM symbol, isused for mapping the PHICHs 0, 1, 2 and 3 (1103). The mini-CCE #37 894,which is obtained by increasing by two an index of the mini-CCE #35 890,which is a dummy mini-CCE for PHICH mapping, in order to select onemini-CCE from the third OFDM symbol, is used for mapping the PHICHs 0,1, 2 and 3 (1103). Therefore, the PHICHs 0, 1, 2 and 3 (1103) aregenerated by selecting 3 mini-CCEs of the mini-CCE #4 881, the mini-CCE#22 893, and the mini-CCE #37 894. Meanwhile, the mini-CCE #35 890disposed in the first OFDM symbol among the dummy mini-CCEs for PHICHmapping, is used for mapping the PHICHs 4, 5, 6 and 7 (1105). Themini-CCE #5 895, which is obtained by increasing by one the index of themini-CCE #4 881, which is a dummy mini-CCE for PHICH mapping, in orderto select one mini-CCE from the second OFDM symbol, is used for mappingthe PHICHs 4, 5, 6 and 7 (1105). Further, the mini-CCE #23 896, which isobtained by increasing by two the index of the mini-CCE #21 886, whichis a dummy mini-CCE for PHICH mapping, in order to select one mini-CCEfrom the third OFDM symbol, is used for mapping the PHICHs 4, 5, 6 and 7(1105). Therefore, the PHICHs 4, 5, 6 and 7 (1105) are generated byselecting 3 mini-CCEs of the mini-CCE #5 895, the mini-CCE #23 896 andthe mini-CCE #35 890.

In summary, if dummy mini-CCEs #A, #B and #C for PHICH mapping areselected, PHICHs a˜a+3 are mapped to mini-CCEs #A, #(B+1) and #(C+2),PHICHs a+4˜a+7 are mapped to mini-CCEs #(A+1), #(B+2) and #C, and PHICHsa+8˜a+11 are mapped to mini-CCEs #(A+2), #B and #(C+1). In this way, onemini-CCE can be selected from each OFDM symbol such that the selectedmini-CCEs are spaced apart from each other on the frequency domain. Whenadditional PHICHs are needed, mini-CCEs for PHICH mapping are selectedby selecting other dummy mini-CCEs and repeating the same process.

Reference numeral 831 shows 32 mini-CCEs, which are rearranged in theorder of the indexes of the mini-CCEs, except for the mini-CCEs used forthe PCFICH and the PHICH. The embodiment generates CCEs from theremaining mini-CCEs 1107, and maps the PDCCH thereto.

Mathematically expressing a PHICH mapping method according to arbitraryL_(PHICH) helps facilitate realization of the method. A method formathematically expressing the PHICH mapping method is described asfollows:

First, a PHICH group should be defined. As described above withreference to the accompanying drawings, multiple PHICHs are transmittedafter undergoing CDM. A set of PHICHs, which are CDM-multiplexed on thesame physical resources, is defined as a PHICH group. If 4 PHICHs aretransmitted after undergoing CDM, PHICH a, PHICH a+1, PHICH a+2 andPHICH a+3 constitute one PHICH group. Additionally, ifIn-phase/Quadrature-phase (I/Q) multiplexing is applied that transmitsdifferent PHICHs on a real component and an imaginary component, 8PHICHs are subjected to CDM, and PHICH a˜PHICH a+7 constitute one PHICHgroup. A PHICH group index g is a value indicating in which PHICH groupa given PHICH is CDM-multiplexed. If a PHICH index is given as p, aPHICH group index can be calculated using Equation (4).g=floor(p/PHICH_GROUP_SIZE)  (4)where PHICH_GROUP_SIZE is a value indicating how many PHICHs areCDM-multiplexed to one PHICH group. When I/Q multiplexing is applied,PHICH_GROUP_SIZE is 8, and otherwise, PHICH_GROUP_SIZE is 4.

Physical resources corresponding to one mini-CCE are enough to transmita CDM-multiplexed PHICH group. However, in order to obtain frequencydiversity gain, the PHICH group is repeatedly transmitted on thefrequency domain N_(PHICH) times, i.e., N_(PHICH) mini-CCEs are used fortransmitting one PHICH group. If N_(PHICH)=3, the PHICH group isrepeatedly transmitted using 3 mini-CCEs. A repetition index is definedby indexing mini-CCEs that transmit one PHICH group, and the repetitionindex r has a value of 0, 1, . . . , N_(PHICH)−1.

For mapping of PHICHs belonging to a PHICH group g, if #A₀(g,0),#A₀(g,1), . . . , #A₀(g,N_(PHICH)−1) disposed on the first OFDM symbolare selected as dummy mini-CCEs, the mini-CCEs to which PHICHs areactually mapped according to L_(PHICH), PHICH group index g, andrepetition index r, are #A(g,0), #A(g,1), . . . , #A(g,N_(PHICH)−1), andA(g,r) is calculated using Equation (5).A(g,r)=A ₀(g,r)+mod(g+r,L _(PHICH))  (5)

In this manner, the PHICH mapping method can be mathematically expressedaccording to arbitrary L_(PHICH). For example, if L_(PHICH)=1, #A₀(g,0),#A₀(g,1), . . . , #A₀(g,N_(PHICH)−1) are mini-CCEs for PHICH mapping. Inthis case, since mod(g+r,L_(PHICH)) becomes 0 regardless of a value of gand r, a desired operation is performed. In addition, if L_(PHICH)=2 or3, operations of FIGS. 23 and 24 are equally performed.

As is apparent from the foregoing description, according to the presentinvention, the OFDM-based mobile communication system can performresource allocation for a control channel in a time-first manner,thereby improving diversity gain.

In the present invention, the resource-mapping for a control channel isperformed by a process of allocating a group of REs, i.e., mini-CCEresources, existing on the 2D domain in a time-first manner using themini-CCE indexing rule, and selecting resources of individual controlchannels according to the resource-mapping rule for a physical channel.The resource-mapping process for a physical channel generates onephysical channel by selecting physical resources having a greater indexgap if possible, and since mini-CCEs are indexed such that as an indexgap is greater, the resources are spaced far apart from each other onthe frequency domain, it is possible to maximally obtain frequencydiversity. Additionally, through the process of first selectingmini-CCEs for the PCFICH, selecting mini-CCEs for the PHICH from theremaining mini-CCEs, generating CCEs using the remaining mini-CCEs, andusing them for the PDCCH, it is possible to guarantee that mini-CCEsoccupied by individual control channels do not collide with each other,i.e., the mini-CCEs are not repeatedly defined.

While the invention has been shown and described with reference to acertain preferred embodiment thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A method for wireless communication, the methodcomprising: mapping control symbols to a plurality of resource elementgroups (REGs) which is not assigned to a physical channel formatindication channel (PCFICH) or a physical hybrid automatic repeatrequest indicator channel (PHICH), the REGs are allocated based on atime first manner; and transmitting the mapped control symbols on apacket dedicated control channel (PDCCH), wherein a number of aplurality of resource elements (REs) in each of the REGs depends on anindex of an orthogonal frequency division multiplexing (OFDM) symbol anda number of configured reference signals.
 2. The method of claim 1,wherein, each of the REGs in a first OFDM symbol of a first slot in asubframe comprises two REs for transmission of a reference signal andfour REs for transmission of a control signal.
 3. The method of claim 1,wherein, in case of one or two reference signals configured, each of theREGs in a second OFDM symbol of the first slot in the subframe comprisesfour REs.
 4. The method of claim 1, wherein, in case of four referencesignals configured, each of the REGs in a second OFDM symbol of thefirst slot in the subframe comprises two REs for transmission of areference signal and four REs for transmission of a control signal. 5.The method of claim 1, wherein each of the REGs in a third OFDM symbolof the first slot in the subframe comprises four REs.
 6. An apparatusfor wireless communication, the apparatus comprising: a controllerconfigured to control operations of: mapping control symbols to aplurality of resource element groups (REGs) which is not assigned to aphysical channel format indication channel (PCFICH) or a physical hybridautomatic repeat request indicator channel (PHICH), the REGs areallocated based on a time first manner; and transmitting the mappedcontrol symbols on a packet dedicated control channel (PDCCH); and atransmitter configured to transmit the mapped control symbols on thePDCCH, wherein a number of a plurality of resource elements (REs) ineach of the REGs depends on an index of an orthogonal frequency divisionmultiplexing (OFDM) symbol and a number of configured reference signals.7. The apparatus of claim 6, wherein each of the REGs in a first OFDMsymbol of a first slot in a subframe comprises two REs for transmissionof a reference signal and four REs for transmission of a control signal.8. The apparatus of claim 6, wherein, in case of one or two referencesignals configured, each of the REGs in a second OFDM symbol of thefirst slot in the subframe comprises four REs.
 9. The apparatus of claim6, wherein, in case of four reference signals configured, each of theREGs in a second OFDM symbol of the first slot in the subframe comprisestwo REs for transmission of a reference signal and four REs fortransmission of a control signal.
 10. The apparatus of claim 6, whereineach of the REGs in a third OFDM symbol of the first slot in thesubframe comprises four REs.
 11. A method for wireless communication,the method comprising: receiving a control signal on a packet dedicatedcontrol channel (PDCCH); and obtaining control symbols mapped to aplurality of resource element groups (REGs) from the received controlsignal, the REGs are not assigned to a physical channel formatindication channel (PCFICH) or a physical hybrid automatic repeatrequest indicator channel (PHICH) and are allocated based on time firstmanner, wherein a number of a plurality of resource elements (REs) ineach of the REGs depends on an index of an orthogonal frequency divisionmultiplexing (OFDM) symbol and a number of configured reference signals.12. The method of claim 11, wherein each of the REGs in a first OFDMsymbol of a first slot in a subframe comprises two REs for transmissionof a reference signal and four REs for transmission of a control signal.13. The method of claim 11, wherein, in case of one or two referencesignals configured, each of the REGs in a second OFDM symbol of thefirst slot in the subframe comprises four REs.
 14. The method of claim11, wherein, in case of four reference signals configured, each of theREGs in a second OFDM symbol of the first slot in the subframe comprisestwo REs for transmission of a reference signal and four REs fortransmission of a control signal.
 15. The method of claim 11, whereineach of the REGs in a third OFDM symbol of the first slot in thesubframe comprises four REs.
 16. An apparatus for wirelesscommunication, the apparatus comprising: a receiver configured toreceive a control signal on a packet dedicated control channel (PDCCH);and a controller configured to control an operation of: obtainingcontrol symbols mapped to resource element groups (REGs) from thereceived control signal, the REGs are not assigned to a physical channelformat indication channel (PCFICH) or a physical hybrid automatic repeatrequest indicator channel (PHICH) and are allocated based on time firstmanner, wherein a number of a plurality of resource elements (REs) ineach of the REGs depends on an index of an orthogonal frequency divisionmultiplexing (OFDM) symbol and a number of configured reference signals.17. The apparatus of claim 16, wherein each of the REGs in a first OFDMsymbol of a first slot in a subframe comprises two REs for transmissionof a reference signal and four REs for transmission of a control signal.18. The apparatus of claim 16, wherein, in case of one or two referencesignals configured, each of the REGs in a second OFDM symbol of thefirst slot in the subframe comprises four REs.
 19. The apparatus ofclaim 16, wherein, in case of four reference signals configured, each ofthe REGs in a second OFDM symbol of the first slot in the subframecomprises two REs for transmission of a reference signal and four REsfor transmission of a control signal.
 20. The apparatus of claim 16,wherein each of the REGs in a third OFDM symbol of the first slot in thesubframe comprises four REs.